import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################



from collections import defaultdict
 
class UnionFind():
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n
 
    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]
 
    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)
 
        if x == y:
            return
 
        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x
 
    def size(self, x):
        return -self.parents[self.find(x)]
 
    def same(self, x, y):
        return self.find(x) == self.find(y)
 
    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]
 
    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]
 
    def group_count(self):
        return len(self.roots())
 
    def all_group_members(self):
        group_members = defaultdict(list)
        for member in range(self.n):
            group_members[self.find(member)].append(member)
        return group_members
 
    def __str__(self):
        return '\n'.join(f'{r}: {m}' for r, m in self.all_group_members().items())
    
n = ni()
a = na()
m = max(a) + 1
uf = UnionFind(m)
b = [i for i in range(m)]

ans = 0
f = []
l = 0
r = m
for i in range(n):
    x = b[uf.find(a[i])] - l
    # print(x)
    if x == 0:
        continue
    ans += 1
    if r - l - x >= x:
        for j in range(l, l + x):
            z = m
            uf.union(j, j + x)
            b[uf.find(j)] = j + x
        l += x
    else:
        # print(l, r, x)
        x = r - l - x
        for j in range(l, l + x):
            # print(j, j + x)
            uf.union(j, j - l + r - x)
            b[uf.find(j)] = j
        r -= x

print(ans)